Mass and Weight MCQs Quiz | Class 9
Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz covers the fundamental concepts of Mass and Weight, including their differences, SI units, scalar vs vector nature, and how weight varies with the acceleration due to gravity (g). Attempt these 10 MCQs to test your understanding, view your score, and download the answer key PDF.
Understanding Mass and Weight
In physics, mass and weight are distinct concepts, although they are often used interchangeably in daily life. This section summarizes the key differences and formulas relevant to Class 9 Science.
1. Key Differences
Mass: Mass is the measure of the quantity of matter contained in a body. It is also a measure of inertia (resistance to change in motion). Mass remains constant regardless of location.
Weight: Weight is the force with which the earth (or any other celestial body) attracts an object towards its center. Weight varies depending on the acceleration due to gravity (g) at that location.
| Property | Mass | Weight |
|---|---|---|
| Definition | Amount of matter | Force of gravity |
| SI Unit | Kilogram (kg) | Newton (N) |
| Quantity | Scalar (Magnitude only) | Vector (Magnitude + Direction) |
| Constancy | Constant everywhere | Changes with ‘g’ |
| Zero Value | Cannot be zero | Can be zero (in space) |
| Measurement | Beam Balance | Spring Balance |
2. Mathematical Relationship
The relationship between weight (W), mass (m), and acceleration due to gravity (g) is given by:
W = m x g
Since the value of ‘g’ on Earth is approximately 9.8 meters per second squared, the weight of a 1 kg mass is 9.8 Newtons.
3. Weight on the Moon
The acceleration due to gravity on the moon is approximately 1/6th of that on the earth. Therefore, the weight of an object on the moon will be 1/6th of its weight on the earth. However, its mass remains exactly the same.
4. Quick Revision List
- Mass is a measure of inertia. Heavier objects have more inertia.
- Weight acts vertically downwards towards the center of the earth.
- At the center of the earth, g is zero, so weight becomes zero.
- In interplanetary space where g is negligible, weightlessness is experienced.
5. Extra Practice Questions
- If an object has a mass of 50 kg on Earth, what is its mass on the Moon? (Ans: 50 kg)
- Calculate the weight of a 10 kg object on Earth (take g = 9.8). (Ans: 98 N)
- Which instrument is used to measure weight directly? (Ans: Spring Balance)
- Is weight a scalar or vector quantity? (Ans: Vector)
- Why does weight change at poles and equator? (Ans: Because ‘g’ varies with radius of earth)
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